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PubMed2003

Encoding predictive reward value in human amygdala and orbitofrontal cortex.

Adaptive behavior is optimized in organisms that maintain flexible representations of the value of sensory-predictive cues. To identify central representations of predictive reward value in humans, we used reinforcer devaluation while measuring neural activity with functional magnetic resonance imaging. We presented two arbitrary visual stimuli, both before and after olfactory devaluation, in a paradigm of appetitive conditioning. In amygdala and orbitofrontal cortex, responses evoked by a predictive target stimulus were decreased after devaluation, whereas responses to the nondevalued stimulus were maintained. Thus, differential activity in amygdala and orbitofrontal cortex encodes the current value of reward representations accessible to predictive cues.

Adult↗

PubMed2004

All-atom folding of the three-helix HIV accessory protein with an adaptive parallel tempering method.

All-atom protein structure prediction from the amino acid sequence alone remains an important goal of biophysical chemistry. Recent progress in force field development and validation suggests that the PFF01 free-energy force field correctly predicts the native conformation of various helical proteins as the global optimum of its free-energy surface. Reproducible protein structure prediction requires the availability of efficient optimization methods to locate the global minima of such complex potentials. Here we investigate an adapted version of the parallel tempering method as an efficient parallel stochastic optimization method for protein structure prediction. Using this approach we report the reproducible all-atom folding of the three-helix 40 amino acid HIV accessory protein from random conformations to within 2.4 A backbone RMS deviation from the experimental structure with modest computational resources.

Computer Simulation↗

PubMed2005

Developmental and functional outcomes at school age of preschool children with global developmental delay.

The later developmental trajectory of young children diagnosed early with global developmental delay was determined. Using a prospective study, preschool children diagnosed with global developmental delay were systematically reassessed during the early school years with standardized developmental and functional outcome measures (Battelle Developmental Inventory and Vineland Adaptive Behavior Scale). Of an original cohort of 99 children assessed and diagnosed at a mean age of 3.4 +/- 1.1 years, 48 were reassessed at a mean age of 7.3 +/- 0.9 years. Group performance on the Battelle Developmental Inventory overall was 66.4 +/- 4.3 (mean 100 +/- 15). Between 75% and 100% of the cohort performed at least 1.5 SD below the normative mean on the individual domains of the Battelle Developmental Inventory. Similarly, the group mean on the Vineland Adaptive Behavior Scale overall was 63.5 +/- 20.8 (mean 100 +/- 15), with between 61% and 76% of the cohort scoring more than 1.5 SD below the mean on each of the domains. Univariate and multivariate analyses on potential predictor variables identified a lack of an underlying etiology as predictive of poorer performance on the Battelle Developmental Inventory fine motor and motor domains and increasing severity of initial delay as predictive of poorer performance on the Vineland Adaptive Behavior Scale communication domain and overall score. Similarly, maternal employment and paternal postsecondary education improved Vineland Adaptive Behavior Scale communication scores, whereas paternal postsecondary education alone predicted better socialization and total scores on the Vineland Adaptive Behavior Scale. Children with early global developmental delay demonstrate persistent and consistently poor performance across all developmental and functional domains. Few variables are apparent at intake to predict later performance.

Child↗

PubMed1995

Simultaneous colour constancy revisited: an analysis of viewing strategies.

We examined whether matching instructions influenced the eye movements that subjects made during a colour constancy experiment. The instructions changed the average duration of exposure to the spectrally biased surround. We also measured the influence that small changes in exposure duration have on the perceived colour. Eye movement and adaptation data were combined to predict differences in colour matches. Two of the five subjects showed an instructional effect that was much larger than that predicted. Analysis of the eye movements, and an experiment with dynamic surrounding colours, reveal that several viewing strategies do not account for the influence of the instruction.

Adaptation, Ocular↗

PubMed2001

Coping-with-hearing-loss model for older adults.

We proposed a coping-with-hearing-loss model that explains how hearing loss, psychosocial factors (i.e., attitudes about aging, personal adjustment to hearing loss, and perceived social support), and perceived strategy effectiveness affect the use of adaptive and maladaptive strategies. Adaptive strategies are behaviors that improve communication (i.e., asking others to repeat). Maladaptive strategies are coping behaviors that do not promote communication (i.e., pretending to understand the conversation). Nonaudiological variables were more important than physical hearing loss (as measured by an audiological examination) in predicting coping behaviors for hearing loss. The use of adaptive strategies was predicted by perceived strategy effectiveness. The use of maladaptive strategies was predicted by perceived effectiveness of the strategies to cope with hearing loss in daily life, poor adjustment to hearing loss, and poor social support. The results suggest that psychosocial issues may need to be addressed when older adults have difficulties coping with their hearing loss.

Adaptation, Psychological↗

PubMed1993

Adaptation to chronic illness: a program of research for testing nursing theory.

The adaptation to chronic illness framework, an elaboration of the Roy adaptation model for chronic illness, provided direction for a program of nursing research. The purposes of investigations within the program were (a) to identify predictors of adaptation to chronic illnesses and (b) to determine whether the relationships between the variables differed by diagnostic group. A total of 597 adults, representing various chronic illness groups, participated in longitudinal studies during a seven-year period. Health-related hardiness and engagement in health promotion activities consistently predicted both physiological and psychosocial adaptation in all chronic illness groups. In addition, the individual's perception of the degree of disability caused by the illness was related to psychosocial functioning. Comparison of adaptive responses between the groups revealed significant differences in physiological adaptation but no significant differences in psychosocial adaptation. Results clarify relationships posited using the theoretical framework and support the value of using nursing models to guide nursing research.

Adaptation, Psychological↗

PubMed1981

Longitudinal spread of adaptation in the rods of the frog's retina.

1. The stimulus-response function of the red rods in the retina of the common frog (Rana temporaria) was determined in different adaptational states by measuring aspartate-isolated receptor responses. 2. Flash stimuli, background adaptations and bleaches were delivered through the same optical channel forming an oblique light-beam striking the receptor side of the isolated and flat-mounted retina at an angle of 10 degrees. 3. When the light was blue-green and optimally polarized the absorbance of the receptor layer was about 2, from which follows that 70-80% of the light was absorbed in the distal third of the rod outer segments, i.e. the exposure was local. Homogeneous exposures of the whole rod outer segments were obtained with orange and red lights. 4. Combinations of homogeneous and local stimuli with homogeneous and local adaptations were used to investigate the longitudinal spread of background, intermediate and opsin adaptation, i.e. the sensitivity-reducing effect of a background light, and the transient and permanent sensitivity losses following a bleach isomerizing 3.5-26% (usually 10%) of the rhodopsin in the retina. 5. The results obtained were related to predictions based both on the assumption that the adaptation effects spread longitudinally within the rod outer segments and the assumption that they are strictly confined to the disks absorbing the adapting lights. 6. These comparisons reveal that all three types of adaptation spread longitudinally. It is for instance clear that the sensitivity loss observed with homogeneous stimuli and local adaptation (as compared to homogeneous adaptation) is larger than that predicted by the non-spreading hypothesis. 7. The longitudinal spread of background adaptation is largely finished within 10 sec after turning on the background light, while an efficient spread of the intermediate adaptation effect may require minutes. 8. A background light decreasing the sensitivity by about one log unit decreases the time from flash to response maximum from 5 to 1 sec (small responses). Corresponding opsin adaptation effects are accompanied by less dramatic changes in response kinetics. 9. Independent of adaptation type - homogeneous or local, background, intermediate or opsin - it was found that local stimuli are less efficient that homogeneous stimuli in light-adapted retinae. This effect can be explained assuming that the sensitivity-reducing effects are pronounced in the distal than in the proximal parts of the rod outer segments. 10. The opsin adaptation effect following 10% local bleaches decreases the sensitivity to both homogeneous and local stimuli 2-3 times more than corresponding homogeneous bleaches. This means that the strength of the opsin effect is not related to the average percentage bleached but to the fraction bleached in the distal part of the rod, or generally to the fraction bleached in the most affected region. 11...

Adaptation, Ocular↗

PubMed2005

Intelligent speed adaptation: accident savings and cost-benefit analysis.

The UK External Vehicle Speed Control (EVSC) project has made a prediction of the accident savings with intelligent speed adaptation (ISA), and estimated the costs and benefits of national implementation. The best prediction of accident reduction was that the fitting on all vehicles of a simple mandatory system, with which it would be impossible for vehicles to exceed the speed limit, would save 20% of injury accidents and 37% of fatal accidents. A more complex version of the mandatory system, including a capability to respond to current network and weather conditions, would result in a reduction of 36% in injury accidents and 59% in fatal accidents. The implementation path recommended by the project would lead to compulsory usage in 2019. The cost-benefit analysis carried out showed that the benefit-cost ratios for this implementation strategy were in a range from 7.9 to 15.4, i.e. the payback for the system could be up to 15 times the cost of implementing and running it.

Accidents, Traffic↗

PubMed2006

The molecular signature of selection underlying human adaptations.

In the last decade, advances in human population genetics and comparative genomics have resulted in important contributions to our understanding of human genetic diversity and genetic adaptation. For the first time, we are able to reliably detect the signature of natural selection from patterns of DNA polymorphism. Identifying the effects of natural selection in this way provides a crucial piece of evidence needed to support hypotheses of human adaptation. This review provides a detailed description of the theory and analytical approaches used to detect signatures of natural selection in the human genome. We discuss these methods in relation to four classic human traits--skin color, the Duffy blood group, bitter-taste sensation, and lactase persistence. By highlighting these four traits we are able to discuss the ways in which analyses of DNA polymorphism can lead to inferences regarding past histories of selection. Specifically, we can infer the importance of specific regimes of selection (i.e. directional selection, balancing selection, and purifying selection) in the evolution of a trait because these different types of selection leave different patterns of DNA polymorphism. In addition, we demonstrate how these types of data can be used to estimate the time frame in which selection operated on a trait. As the field has advanced, a general issue that has come to the forefront is how specific demographic events in human history, such as population expansions, bottlenecks, and subdivision of populations, have also left a signature across the genome that can interfere with our detection of the footprint of selection at particular genes. Therefore, we discuss this general problem with respect to the four traits reviewed here, and describe the ways in which the signature of selection can be teased from a background signature of demographic history. Finally, we move from a discussion of analyses of selection motivated by a "candidate-gene" approach, in which a priori information led to the analysis of specific gene, to discussion of "genome-scanning" approaches that are directed at discovering new genes that have been under positive selection. Such scans can be designed to detect those genes that have been positively selected in our divergence from chimpanzees, as well as those genes that have been under selection as human populations have migrated, differentiated, and adapted to specific geographic environments. We predict that both approaches will be applied in the future, enabling a greater insight into human species-wide adaptations, as well as the specific adaptations of human populations.

Animals↗

PubMedDate not supplied

Ocular discomfort at the initial wearing of rigid gas permeable contact lenses.

PURPOSE: To evaluate the relationship between ocular discomfort in the initial wearing of rigid gas permeable contact lenses (RGPCL) and the time required to adapt to RGPCL as measured by using the visual analogue scale (VAS). METHODS: RGPCL were prescribed for 89 patients (178 eyes) with myopia or myopic astigmatism and no history of wearing contact lenses. The patients who stopped wearing RGPCL after 1 week because of ocular discomfort were defined as dropouts, and those who adapted to regular full-time RGPCL wear were defined as successful wearers. VAS scores were measured at several intervals for 1 month after the initial wearing of the lenses. The number of days required to adapt to wearing RGPCL was defined as the adaptation time. RESULTS: Four patients were dropouts due to ocular discomfort (eight eyes; 4.5%). VAS scores were significantly lower in successful wearers than in dropouts at 1 week, although their VAS scores were not different at 1 day. VAS scores of the successful wearers at 1 week were significantly lower than those at 1 day. The average time required to adapt to RGPCL was 23.0 +/- 22.1 days for the 85 successful wearers. Lower VAS scores at 1 day or 1 week were significantly correlated with a shorter adaptation time in the successful RGPCL wearers. CONCLUSIONS: Our results indicate that the VAS score might be useful for predicting successful RGPCL use and the adaptation time required by successful wearers.

Adaptation, Ocular↗

PubMed1991

Prediction of gas chromatographic relative retention times of stimulants and narcotics.

The ADAPT software system was used to create models for the prediction of gas chromatographic relative retention times (RRTs) of stimulants and narcotics that are analyzed in doping control of athletes. The two main methods that were followed for building the models were the quantitative structure-retention relationship (QSRR) and multiple linear regression analysis. The main proposed model for the entire data set had a multiple correlation coefficient R = 0.991 and standard error s = 0.046 or approximately 4.5%. Because of the relatively high standard error of the main model, a second model was built on a subset of compounds with R = 0.982 and s = 0.027 or approximately 2.5%.

Central Nervous System Stimulants↗

PubMedDate not supplied

[Assessment of the Life Skills Profile and the Brief Psychiatric Rating Scale as predictors of the length of psychiatric hospitalization].

INTRODUCTION: Length of hospital stay is generally used as an indirect indicator of effectiveness and efficiency of treatment programs, but it is uncommon that other factors related with hospital stay are also contemplated. The aims of this study are to analyse the relationship between illness severity and adaptative behavior and to assess the predictive power of both constructs on the length of hospital stay. METHODS: Multicenter prospective study (n = 132). The outcome variable is the length of hospital stay cut off at 90 days. The illness severity (BPRS) and the adaptative behavior (LSP) of psychiatric patients are explanatory variables. RESULTS: After adjusting for age, gender and psychiatric diagnosis, negative symptoms (OR = 2.3; 95%CI = 1.3 4.1), self-competence (OR = 0.85; 95% CI = 0.78 0.93), and the total LSP score (OR = 0.96; 95% CI = 0.93 0.98), were significantly associated to the length of hospital stay. These three variables shared a similar predictive power (chi2 = 1.9 on 2 d.f.; P = 0.4). CONCLUSION: Deficits in adaptative behaviour are as relevant as negative symptoms to explain the length of hospital stay. Both assessment domains should be included in the administrative information at discharge.

Activities of Daily Living↗

PubMed1991

[Status of the cardiovascular system of the fetus and newborn infant in different degree of severity of maternal hypertensive syndrome].

Examinations of 260 pregnant women with hypertensive syndromes and their 60 full-term newborns, carried out with the use of echography of the umbilical artery, umbilical vein, aorta, and internal carotid artery of the fetus have demonstrated a high informative value of these methods for the assessment of the type of fetal condition and prediction of the newborn's adaptive mechanisms of the cardiovascular system. Significant changes of the cardiovascular system were revealed in small-for-date fetuses and in chronic fetal hypoxia, as well as functional changes in the newborns of the mothers with the hypertensive syndrome, with born signs of intrauterine suffering. These changes should be borne in mind when predicting the development of infants born of mothers with the hypertensive syndrome.

Echocardiography, Doppler↗

PubMed1997

The psychosocial impact of the diagnosis and treatment of laryngeal cancer.

The diagnosis and treatment of laryngeal cancer involves psychosocial stress for most patients because the disease can be life threatening and treatment is potentially disfiguring. Loss of voice, appearance changes, and functional limitations all pose threats to self image and identity. Since voice is essential to psychological identity, laryngectomy may pose significant short- and long-term adjustment problems. Risk for psychological disturbance and problems at the initiation of treatment and adaptation following treatment can be predicted based on certain patient information. The integration of a multidisciplinary team at the outset of treatment planning is crucial in helping patients adjust to the impact of laryngeal cancer.

Adaptation, Psychological↗

PubMed2004

Sequence-based prediction of pathological mutations.

The development of methods to assess the impact of amino acid mutations on human health has become an important goal in biomedical research, due to the growing number of nonsynonymous SNPs identified. Within this context, computational methods constitute a valuable tool, because they can easily process large amounts of mutations and give useful, almost cost-free, information on their pathological character. In this paper we present a computational approach to the prediction of disease-associated amino acid mutations, using only sequence-based information (amino acid properties, evolutionary information, secondary structure and accessibility predictions, and database annotations) and neural networks, as a model building tool. Mutations are predicted to be either pathological or neutral. Our results show that the method has a good overall success rate, 83%, that can reach 95% when trained for specific proteins. The methodology is fast and flexible enough to provide good estimates of the pathological character of large sets of nonsynonymous SNPs, but can also be easily adapted to give more precise predictions for proteins of special biomedical interest.

Databases, Protein↗

PubMed2005

Dosimetric impact of geometric errors due to respiratory motion prediction on dynamic multileaf collimator-based four-dimensional radiation delivery.

The synchronization of dynamic multileaf collimator (DMLC) response with respiratory motion is critical to ensure the accuracy of DMLC-based four dimensional (4D) radiation delivery. In practice, however, a finite time delay (response time) between the acquisition of tumor position and multileaf collimator response necessitates predictive models of respiratory tumor motion to synchronize radiation delivery. Predicting a complex process such as respiratory motion introduces geometric errors, which have been reported in several publications. However, the dosimetric effect of such errors on 4D radiation delivery has not yet been investigated. Thus, our aim in this work was to quantify the dosimetric effects of geometric error due to prediction under several different conditions. Conformal and intensity modulated radiation therapy (IMRT) plans for a lung patient were generated for anterior-posterior/posterior-anterior (AP/PA) beam arrangements at 6 and 18 MV energies to provide planned dose distributions. Respiratory motion data was obtained from 60 diaphragm-motion fluoroscopy recordings from five patients. A linear adaptive filter was employed to predict the tumor position. The geometric error of prediction was defined as the absolute difference between predicted and actual positions at each diaphragm position. Distributions of geometric error of prediction were obtained for all of the respiratory motion data. Planned dose distributions were then convolved with distributions for the geometric error of prediction to obtain convolved dose distributions. The dosimetric effect of such geometric errors was determined as a function of several variables: response time (0-0.6 s), beam energy (6/18 MV), treatment delivery (3D/4D), treatment type (conformal/IMRT), beam direction (AP/PA), and breathing training type (free breathing/audio instruction/visual feedback). Dose difference and distance-to-agreement analysis was employed to quantify results. Based on our data, the dosimetric impact of prediction (a) increased with response time, (b) was larger for 3D radiation therapy as compared with 4D radiation therapy, (c) was relatively insensitive to change in beam energy and beam direction, (d) was greater for IMRT distributions as compared with conformal distributions, (e) was smaller than the dosimetric impact of latency, and (f) was greatest for respiration motion with audio instructions, followed by visual feedback and free breathing. Geometric errors of prediction that occur during 4D radiation delivery introduce dosimetric errors that are dependent on several factors, such as response time, treatment-delivery type, and beam energy. Even for relatively small response times of 0.6 s into the future, dosimetric errors due to prediction could approach delivery errors when respiratory motion is not accounted for at all. To reduce the dosimetric impact, better predictive models and/or shorter response times are required.

Fluoroscopy↗

PubMed2004

The 24-h growth hormone rhythm in men: sleep and circadian influences questioned.

The 24-h rhythm of growth hormone (GH) is thought to be controlled primarily by sleep processes with a weak circadian component. This concept has been recently questioned in sleep-deprived persons. To test the notion of a high sleep-dependency of GH release, we established simultaneous 24-h rhythms of GH and melatonin, a circadian marker, in night workers who form a model for challenging sleep and circadian processes. Ten day-active subjects and 11 night workers were studied during their usual sleep-wake schedule, with sleep from 23:00 to 07:00 hours and 07:00 to 15:00 hours, respectively. Experiments were conducted in sleep rooms under continuous nutrition, bed rest, and dim light. Melatonin and GH were measured every 10 min over 24 h. In day-active subjects, melatonin and GH showed the well-known 24-h profiles, with a major sleep-related GH pulse accounting for 52.8 +/- 3.5% of the 24-h GH production and the onset of the melatonin surge occurring at 21:53 hours +/- 18 min. In night workers, melatonin showed variable circadian adaptation, with the onset of secretion varying between 21:45 and 05:05 hours. The sleep-related GH pulse was lowered, but the reduction was compensated for by the emergence of large individual pulses occurring unpredictably during waking periods, so that the total amount of GH secreted during the 24 h was constant. One cannot predict the degree of GH adaptation from the highly variable melatonin shift. These results argue against the concept that sleep processes exert a predominant influence on GH release whatever the conditions. When sleep and circadian processes are misaligned, the blunting of the sleep-related GH pulse is counteracted, as in sleep-deprived persons, by a compensatory mechanism promoting GH pulses during wakefulness.

Adaptation, Physiological↗

PubMed2006

A single system explains human speed perception.

Motion is fully described by a direction and a speed. The processing of direction information by the visual system has been extensively studied; much less is known, however, about the processing of speed. Although it is generally accepted that the direction of motion is processed by a single motion system, no such consensus exists for speed. Psychophysical data from humans suggest two separate systems processing luminance-based fast and slow speeds, whereas neurophysiological recordings in monkeys generally show continuous speed representation, hinting at a single system. Although the neurophysiological findings hint at a single system, they remain inconclusive as only a limited amount of cells can be measured per study and, possibly, the putative different motion systems are anatomically separate. In three psychophysical motion adaptation experiments, we show that predictions on the basis of the two-motion system hypothesis are not met. Instead, concurrent modeling showed that both here-presented and previous data are consistent with a single system subserving human speed perception. These findings have important implications for computational models of motion processing and the low-level organization of the process.

Adaptation, Physiological↗